Passage Summary: Tuna is treated with carbon monoxide to keep it looking pink and fresh. The chemical itself won't hurt you, but for some reason, this process makes it more likely that people will get sick from eating the fish.

Reasoning: Treating tuna with carbon monoxide is not inherently harmful, yet it increases the likelihood of people becoming ill from eating it.

Analysis: The paradox here is a classic 'hidden danger' scenario. We have a harmless treatment (carbon monoxide) that leads to a harmful outcome (sickness). To resolve this, we need a bridge that explains how the *effect* of the treatment—keeping the fish from turning brown—tricks the consumer. Since browning is a natural indicator of spoilage, look for an answer that suggests the treatment allows old, spoiled fish to look deceptively fresh. The sickness isn't coming from the gas; it's coming from the rotten fish that people are now eating because it still looks good.